In people with IBS, one (or more) of these sugars might be poorly absorbed in the small intestine. As a result, these sugars move to the large intestine where bacteria feed on them (releasing gas). In addition, some sugars also pull in water.

So, let’s take a look at each of the fermentable sugars more closely.

The different FODMAP types are based on carbohydrate chain length.

Oligosaccharides

This group includes the galacto-oligosaccharides (GOS) and fructans. These have the longest chain length. Humans cannot digest GOS and fructans. As such, they are highly fermentable (broken down by our gut bacteria), and produce gas. Consequently, this results in symptoms of bloating and pain in sensitive people.

Found in: Wheat, rye, legumes, nuts, artichokes, onion and garlic.

Disaccharides

The disaccharide referred to is lactose. We require an enzyme called lactase to digest lactose. Lactase can be lower in Asian and Mediterranean populations, in older people and during gut inflammation. However, many people have adequate lactase to digest lactose so do not need to remove lactose from their diet, even when undertaking a low-FODMAP diet.

Found in: Milk products, small amounts in yoghurt, cheese.

Monosaccharides

The monosaccharide referred to is fructose. The amount of fructose that is poorly absorbed is small. However, fructose is absorbed slowly, and pulls water into the bowel. As a result, this can cause bloating and pain, and when taken in large amounts it may also cause diarrhoea.

Found in: Apples, pears, watermelon, honey and some vegetables, packaged foods and beverages.

and…

Polyols

The main polyols referred to are sorbitol and mannitol (others include xylitol, isomalt etc.). Like fructose, polyols absorb slowly and draw in water.

Found in: Apples, pears, stone fruit, cauliflower, mushrooms and snow peas. Additionally, polyols are used in sugar-free mints and gum.

Finally, note that many foods actually contain a combination of several FODMAPs! So, if you think you might be experiencing symptoms of IBS – see your doctor and a dietitian skilled in low-FODMAPs, and check out our online fodmap challenge!